Nail penetration testing is known as testing for evaluating safety when a battery is broken from the outside. Nail penetration testing is testing of penetrating a conductive nail through a battery, and observing temperature rising etc. when internal short circuits occur in its electric elements.
Patent Literature 1 discloses an electrolyte solution based battery comprising a plurality of power generation elements that are electrically connected in series via bipolar electrodes, and external short circuit members that are provided outside the power generation elements, wherein the electric resistance of current collectors of a power generation element is lower than that of conductive materials of an external short-circuit member. Patent Literature 1 describes that in nail penetration testing, the power from the power generation elements is consumed by short circuits of the external short-circuit members, which can lead to suppression of heat generation due to internal short circuits in the power generation elements. Patent Literatures 2 to 4 also disclose various techniques for suppressing heat generation caused by internal short circuits of a battery.